The present invention relates generally to medical balloons made at least in part from polytetrafluoroethylene.
The use of medical balloons for dilatation of a body vessel as well as for expansion and seating of a medical devices such as a stent is well known. Medical balloon may be made of a single layer of material or of multiple layers of material. In the case of multilayer balloons, the multiple layers may be of the same or different materials.
A variety of materials have been used for making medical balloons including thermoplastic polyurethanes (TPU), polyethylene, polyesters such as polyethylene terephthalate (PET) including non-compliant PET, Arnitel, Hytrel, polyetherether ketone (PEEK), block copolymers of polyether polymers and polyamides (polyether block amides) such as Pebax(copyright) (all grades) available from Elf Atochem North America, block copolymers of polyether and polyester polymers such as Hytrel(copyright) available from E. I. DuPont de Nemours and Co. in Wilmington, Del., Teflon(copyright), polyamides such as nylon-11 and nylon-12, block polyimides, polytetrafluoroethylene (PTFE), polyolefins such as polyethylenes (PE) and polypropylenes (PP), synthetic rubbers including SBR and EPDM, as well as other polyolefins and silicone elastomers. For catheter balloons used in coronary angioplasty preferred polymeric substrates are PET, nylon and PE. The specific choice of materials depends on the desired characteristics of the balloon.
Of these materials, PTFE is of interest for use in medical balloons because of its low coefficient of friction, chemical resistance, flexibility and strength. Because of the physical properties of PTFE, however, the material cannot be processed in the same way that conventional thermoplastic elastomers are processed.
The use of polytetrafluoroethylene (PTFE) and expanded PTFE (EPTFE) in implantable medical devices such as balloons has been disclosed in U.S. Pat. No. 5,752,934 and U.S. Pat. No. 5,868,704 both of which disclose a balloon comprised of a porous EPTFE layer and an elastomeric or inelastic layer. The EPTFE films may serve either as a coat for a balloon or as an integral part of a balloon in the form of an outer layer. The balloons disclosed therein are formed from a helically wound porous EPTFE film. In one example, twenty layers of EPTFE film are used to form the EPTFE portion of the balloon. As a result, these balloons tend to have a large profile.
It is desirable to produce a medical balloon which has some of the properties of a PTFE balloon and yet has a low profile. More specifically, it is a goal of the present invention to provide a non-compliant EPTFE balloon which has a high burst strength and the ability to return to its preinflation diameter following repeated inflation/deflation cycles. To that end, the present invention provides medical balloons having one or more EPTFE layers disposed between an inner balloon material and an outer balloon material.
All US patents and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
The present invention is directed to medical balloons comprising EPTFE and similar materials as well as to catheters with such balloons mounted thereon. At least a portion of the medical balloon disclosed herein includes an inner layer, an intermediate layer and an outer layer. The intermediate layer disposed between the inner and outer layers is formed of EPTFE. A wide variety of materials may be used for the inner and outer layers including thermoplastic materials, elastomeric materials and thermoplastic elastomeric materials.
The intermediate expanded PTFE layer may extend over the entire length of the balloon or may extend over only a portion of the balloon.
The present invention is also directed to a balloon having a first body portion with a generally linear compliance curve to burst pressure and a second body portion having a stepped compliance curve.
The balloons of the present invention may be formed in a variety of ways including coating the interior and exterior of an EPTFE tube with first and second materials or laminating an inner and an outer layer of material to one or more layers of EPTFE at a suitable temperature. Alternatively, the balloon may be formed by inserting a PTFE or an EPTFE tube between inner and outer tubes of other materials and suitably shaping the tubes at a desired temperature via the application of tension and/or radially outward pressure such as by blowing. Where a PTFE tube is used, the PTFE may be expanded during the step of radially expanding the tube so as to form an EPTFE tube. The EPTFE tube may also be formed by expanding an extruded tube of PTFE separate from radial expansion or may be formed of a sheet of EPTFE that is disposed in a tubular form.
The present invention is also directed to methods of preparing the inventive balloon. One such method involves coating a tube of PTFE or EPTFE on the inside and outside. Another method involves concentrically disposing inner, outer and intermediate tubes and joining the tubes together via lamination or heating or any other suitable technique. Yet another method involves co-extruding the three or more layers of balloon material.
The inventive catheters include the medical balloon disclosed herein disposed about a tube and having an inflation lumen in fluid communication with the balloon. The inventive catheter may be dilatation catheters, a medical device delivery catheter or any other catheter that carries a medical balloon.